Conventionally, many semiconductor integrated circuit devices (hereinafter “ICs (integrated circuits)”) that drive power transistors, such as power supply devices and motor driving devices, incorporate an overheat protection circuit (a so-called thermal shutdown circuit) for preventing the breakdown of the ICs (in particular, the power transistors thereof) due to an abnormal rise in temperature of the ICs (see Patent Documents 1 and 2, which the applicant of the present invention once filed). The aforementioned overheat protection circuit is so configured as to generate an overheat protection signal by exploiting the property that Vf (the base-emitter forward voltage drop) of a bipolar transistor varies in general depending on the ambient temperature.
Patent Document 1: JP-A-2004-253936
Patent Document 2: JP-B-H06-16540